Page:Popular Science Monthly Volume 45.djvu/365

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349
LATITUDE AND VERTEBRÆ.

inclosed waters, and in the waters of past geological epochs, the process would be less completed, the numbers of vertebræ would be larger, while the individual vertebra? remain smaller, less complete, and less perfectly ossified.

This, in a general way, is precisely what we do find in examining the skeletons of a large variety of fishes.

The life of the tropics, so far as fishes are concerned, offers many analogies to the life of cities, viewed from the standpoint of human development. In the cities in general, the conditions of individual existence for the man are most easy, but there also competition of life is most severe. The struggle for existence is not a struggle with the forces and conditions of Nature. It is not a struggle with wild beasts, unbroken forests, or stubborn soil, but a competition between man and man for the opportunity of living.

It is in the city where the influences which tend to modernization and concentration of the characters of the species go on most rapidly. It is adaptation or death to each individual in the city: every quality not directly useful tends to become lost or atrophied.

Conversely, it is in the "backwoods," the region farthest from human conflicts, where primitive customs, antiquated peculiarities, and useless traits are longest and most persistently retained. The life of the "backwoods" may be not less active or vigorous, but it will lack specialization. It is from the unused possibilities of the "backwoods" that the progress of the future comes. The high specialization of favored regions unfits its subjects for life under changed conditions. The loss of muscular power is often one of the results of skeletal specialization.

The coral reef is the metropolis of the fish. The deep sea, the arctic sea, and the isolated rivers—these are the ichthyological backwoods.

An exception to the general rule in regard to the numbers of vertebræ is found in the case of the eel. Eels inhabit nearly all seas, and everywhere they have many vertebræ. The eels of the tropics are at once more specialized and more degraded. They are better eels than those of northern regions, but, as the eel is a degraded type, they have gone further in the loss of structures in which this degeneration consists.

It is not well to push this analogy too far, but perhaps we can find in the comparison of the tropics and the cities some suggestion as to the development of the eel.

In the city there is always a class which follows in no degree the general line of development. Its members are specialized in a wholly different way. By this means they take to themselves a field which others have neglected, making up in low cunning what they lack in humanity or intelligence.